Preventing Viral Replication
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Questions and Answers

What is the primary way that a host cell can recognize the presence of a virus?

  • Recognizing the microbe-associated immunostimulants on the surface of the virus
  • Measuring the size of the virus
  • Identifying the virus's surface proteins
  • Detecting unusual elements of the viral genome, such as double-stranded RNA (correct)

    • What is the role of the enzyme Dicer in the response to viral infection?

  • To synthesize double-stranded RNA
  • To degrade double-stranded RNA into small fragments (correct)
  • To bind to single-stranded RNA
  • To translate viral RNA into protein

    • What is the outcome of the binding of double-stranded RNA fragments to single-stranded RNA in the host cell?

  • The formation of a double-stranded RNA complex
  • The activation of innate immune responses
  • The synthesis of new viral proteins
  • The destruction of the single-stranded RNA (correct)

    • What are the two cytokines produced and secreted by the host cell in response to viral infection?

    <p>Interferon-a and interferon-b</p> Signup and view all the answers

    What is the length of the double-stranded RNA fragments produced by the enzyme Dicer?

    <p>About 21-25 nucleotide pairs</p> Signup and view all the answers

    What is the first step in the program of intracellular responses to eliminate viral RNA?

    <p>The degradation of double-stranded RNA into small fragments</p> Signup and view all the answers

    Why are mammalian cells particularly adept at recognizing the presence of double-stranded RNA?

    <p>Because they have a highly effective innate immune response</p> Signup and view all the answers

    What is the effect of interferons on protein synthesis in the host cell?

    <p>It shuts down most protein synthesis by phosphorylating and inactivating eIF-2</p> Signup and view all the answers

    What is the purpose of the host cell's self-destruction by apoptosis?

    <p>To prevent the virus from replicating</p> Signup and view all the answers

    What is the function of the protein encoded by the influenza virus?

    <p>To block the recognition of dsRNA by Dicer</p> Signup and view all the answers

    What is the role of natural killer cells in the innate immune system?

    <p>To recognize and eliminate infected cells</p> Signup and view all the answers

    What is the effect of some viruses on host cell apoptosis?

    <p>They inhibit apoptosis, which can have the side-effect of promoting cancer</p> Signup and view all the answers

    What is the outcome when the host cell's measures to inhibit viral replication fail?

    <p>The cell takes the extreme step of killing itself by apoptosis</p> Signup and view all the answers

    What is the effect of interferons on viral RNA?

    <p>They non-specifically degrade ssRNA</p> Signup and view all the answers

    What is the common mechanism of killing infected target cells by NK cells and cytotoxic T lymphocytes?

    <p>Inducing apoptosis</p> Signup and view all the answers

    What is the primary function of dendritic cells in the innate immune system?

    <p>To recognize and phagocytose invading pathogens</p> Signup and view all the answers

    What is the result of dendritic cells cleaving pathogen proteins into peptide fragments?

    <p>The fragments bind to MHC proteins</p> Signup and view all the answers

    What is the mechanism by which NK cells and cytotoxic T cells destroy virus-infected cells?

    <p>By inducing apoptosis in the infected cells</p> Signup and view all the answers

    What is the location where activated dendritic cells activate T cells?

    <p>In a nearby lymphoid organ</p> Signup and view all the answers

    What is the role of co-stimulatory proteins displayed on activated dendritic cells?

    <p>To activate T cells</p> Signup and view all the answers

    What type of cell surface proteins do NK cells and cytotoxic T cells recognize to detect virus-infected cells?

    <p>Class I MHC proteins</p> Signup and view all the answers

    How do cytotoxic T cells recognize virus-infected cells?

    <p>By recognizing peptide fragments of viral proteins bound to class I MHC proteins</p> Signup and view all the answers

    What do cytokines secreted by activated dendritic cells influence?

    <p>The type of response made by T cells</p> Signup and view all the answers

    Why do many viruses inhibit the expression of class I MHC proteins on the surface of infected cells?

    <p>To avoid detection by cytotoxic T cells</p> Signup and view all the answers

    What is the outcome of the interaction between activated dendritic cells and T cells?

    <p>The T cells are activated to fight the pathogen</p> Signup and view all the answers

    Which of the following viruses encodes proteins that block class I MHC gene transcription?

    <p>Adenovirus and HIV</p> Signup and view all the answers

    What is the role of MHC proteins in the process of antigen presentation?

    <p>To carry peptide fragments to the cell surface</p> Signup and view all the answers

    What is the main difference between how cytotoxic T cells and NK cells recognize virus-infected cells?

    <p>Cytotoxic T cells recognize peptide fragments of viral proteins, while NK cells recognize the level of class I MHC proteins</p> Signup and view all the answers

    What is the link between the innate and adaptive immune systems provided by?

    <p>Dendritic cells</p> Signup and view all the answers

    What is the outcome of NK cells selectively killing host cells that express low levels of class I MHC proteins?

    <p>The virus-infected cells and some cancer cells are selectively eliminated</p> Signup and view all the answers

    What is the primary function of pattern recognition receptors on dendritic cells?

    <p>To recognize and phagocytose invading pathogens</p> Signup and view all the answers

    What is the purpose of the co-stimulatory proteins displayed on activated dendritic cells?

    <p>To activate T cells of the adaptive immune system</p> Signup and view all the answers

    What is the outcome of the interaction between dendritic cells and pathogens?

    <p>The dendritic cells are activated and phagocytose the pathogens</p> Signup and view all the answers

    What is the role of MHC proteins in the process of antigen presentation?

    <p>To carry the peptide fragments to the cell surface</p> Signup and view all the answers

    Where do activated dendritic cells activate T cells?

    <p>In the lymphoid organs such as lymph nodes</p> Signup and view all the answers

    What is the outcome of the activation of T cells by dendritic cells?

    <p>The T cells are activated and join the battle against the specific invader</p> Signup and view all the answers

    What is the role of cytokines secreted by activated dendritic cells?

    <p>To influence the type of response that the T cells make</p> Signup and view all the answers

    What is the mechanism by which dendritic cells recognize and respond to pathogens?

    <p>Through the recognition of pattern recognition receptors and the activation of T cells</p> Signup and view all the answers

    What is the link between the innate and adaptive immune systems provided by?

    <p>Dendritic cells</p> Signup and view all the answers

    What is the outcome of the battle between the host and the pathogen?

    <p>The outcome depends on the specific pathogen and the host's immune response</p> Signup and view all the answers

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